Extracorporeal membrane oxygenation: (ECMO) A life support system that circulates the blood through an oxygenating system. ECMO is like a heart-lung machine that takes over the work of the heart and lungs during open heart surgery. ECMO may be used, for example, to treat ARDS (acute respiratory distress syndrome), lethal smoke inhalation injury, or irreversible heart failure. As a general rule, ECMO is only used for limited time because of the high risks of bleeding, clotting, infection and organ failure.